In the mechanical design of computer systems, it has been the practice to partition the system into at least two separate components, namely a video display monitor and a system box, connected by a cable. The monitor is commonly an assembly having a cathode-ray tube (CRT) or other video display, a power supply, high-voltage electronics to drive the display, and a small amount of relatively low-voltage electronics. The CRT and the high-voltage electronics are commonly referred to collectively as the video display components; they work together to display image data which is received by the low-voltage electronics from the system box via the cable.
The system box in a computer system might contain, for example, a microprocessor, memory, a disk drive, a power supply, and other circuitry. The collection of these components in the system box is commonly referred to as the processor subsystem. The processor subsystem runs software programs, accesses files stored on the disk drive, and responds to user input from a keyboard or mouse attached to the system box. The processor subsystem in the system box communicates with the monitor over a cable in order to display the results of its operations.
In the past, partitioning the system in two boxes as described above was advantageous for several reasons. The video display components in the monitor operate at dangerously high voltages, while the processor subsystem operates at lower voltages which are relatively safe. Since the processor subsystem is often customer-accessible for memory or disk upgrades, it should therefore be isolated from the high-voltage video display components for reasons of customer safety. Also, the electromagnetic interference (EMI) generated by the video display components could interfere with the operation of the processor subsystem, or vice-versa, so it has been beneficial to house them in separate EMI-shielded enclosures.
While the two-box approach to computer system design thus has technical advantages, it nevertheless imposes costs as well. There is the obvious cost of two enclosures, as well as two power supplies, power switches and power cords. There are also cables and connectors on each box merely to enable them to communicate with each other. All of these components add to the cost of the computer system. Additionally, the computer system must be packaged into two shipping containers, and thus is more expensive to ship.
The costs associated with a two-box system partition can be particularly burdensome in a small computer system which is meant to be sold in a price-sensitive market. Therefore it is desirable to reduce or eliminate excess costs while retaining the beneficial EMI and safety features of a two-box system.